State the codec each Spark value travels in, a box's among them

README.md

@@ -104,9 +104,11 @@ SparkSession spark = SparkSession.builder().appName("mobilityspark").master("loc
 GeneratedSpatioTemporalUDFs.registerAll(spark);
 ```
 
-Temporal values, spans, span sets and sets travel as their MEOS WKB bytes, a binary column, and a
-column of their hex-WKB text reads as well; geometries travel as WKT or EWKT text, and boxes,
-circular buffers, network points and poses as their text form:
+A value travels in the codec the MEOS catalog states for its type: temporal values, spans, span
+sets, sets, boxes, circular buffers, network points and poses as their MEOS WKB bytes, a binary
+column, read as well from their hex-WKB text and, for a type with a generic text reader such as a
+box, from their text form; geometries travel as EWKT and are read from WKT or EWKT, and network
+segments and JSON as their text form:
 
 ```sql
 -- accessors under their canonical MobilityDB SQL names

src/test/java/org/mobilitydb/spark/GeneratedSurfaceTest.java

@@ -283,6 +283,12 @@ void values_travel_as_wkb_and_hex_wkb_stays_readable() {
         assertTrue(t instanceof byte[], "a temporal travels as WKB, got " + t.getClass());
         Object span = scalar("SELECT timeSpan(" + tint + ")");
         assertTrue(span instanceof byte[], "a span travels as WKB, got " + span.getClass());
+        // A box travels as its WKB bytes too, and is read from those bytes and from its text.
+        String box = "'STBOX X((1,1),(2,2))'";
+        Object stbox = scalar("SELECT stbox_in(" + box + ")");
+        assertTrue(stbox instanceof byte[], "a box travels as WKB, got " + stbox.getClass());
+        assertEquals("STBOX X((1,1),(2,2))", scalar("SELECT stbox_out(stbox_in(" + box + "), 15)"));
+        assertEquals(Boolean.FALSE, scalar("SELECT hasZ(" + box + ")"));
         // The bytes and the hex-WKB text of one value answer alike.
         assertEquals(3, ((Number) scalar("SELECT numInstants(" + tint + ")")).intValue());
         assertEquals(3, ((Number) scalar("SELECT numInstants('" + TINT_HEX + "')")).intValue());